Optical disc apparatus

ABSTRACT

An optical disc apparatus includes a pause circuit for pausing data encoders upon receiving a pause signal so that a write operation may be paused without writing dummy data, thereby maintaining data succession. The optical disc apparatus also includes a circuit for accurately determining a write start location by referring to previously written data. A processor generates a pause signal when the amount of data in the optical drive apparatus data buffer is low, and removes the pause signal when additional data from a host is received. The processor may also automatically reduce the write speed of the optical disc apparatus upon a pause condition, thereby preventing the necessity for excessive pausing.

[0001] The instant application is a continuing application ofapplication Ser. No. 09/741,900, now allowed, the entire disclosure ofwhich is incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an optical disc drive whichrecords and reproduces information for an optical disc like a CD-R mediaor a CD-RW media.

[0004] 2. Description of the Related Art

[0005] The recording format of a CD-R or CD-RW optical disc isprescribed in the Orange Book, an industry standard. The Orange Bookrules dictate that data sectors which are not consecutively writtenrequire lengthy lead-in and lead-out sectors such as Link, Run-In, andRun-Out sectors. These sectors are necessary to enable optical discdrives to synchronize to the data on the optical media. This is becausethe laser beam must be repositioned each time a new writing session isstarted, and known optical disc drive positional controls are notsufficiently accurate to position a laser beam at the exact end point ofpreviously written data.

[0006] Therefore, conventional optical disc drives need to write data onan entire track, known as Track-at-Once, or an entire disc, known asDisc-at-Once, continuously in order to avoid adding lead-in and lead-outsectors. In other words, known optical disc drives must write the entiredisc or track in a single writing session.

[0007] Conventional optical disc drives employ Cross-InterleavedReed-Solomon Code (CIRC) encoding which is performed by a CD encoderchip. The CD encoder chip automatically encodes the data in a bufferwhich temporarily stores data from a host while waiting for the data tobe encoded and written to an optical media. Another reason thatconventional optical disc drives must write data in a single session isthat the CD encoder chip will continue to generate dummy data even ifthe buffer containing data from the host becomes empty. Continuity ofdata, or data succession, is lost by inserting and writing dummy data ina head where data from a preceding sector was recorded.

[0008] Because conventional disc drives need to write an entire track ordisc in a single session, a problem is encountered if the flow of datafrom the host computer to the optical disc drive buffer is interrupted.Since CD-R and CD-RW optical discs are write-once media, a write failureresults in the loss of expensive media.

[0009] The problem of maintaining data from the host in the optical discdrive buffer is severe when the writing speed of the optical disc driveis high. Because the data size of a track or disc is large compared tothe optical disc buffer size, if the data transfer rate between the hostcomputer and the optical drive is even slightly slower than the speed atwhich data is written to the optical disc, or data transfer between thehost and the optical disc drive is interrupted for even a short period,the buffer may go empty. This problem is known as Buffer Run.

[0010] Because hosts transmit data at varying rates, some optical discdrives include a test mode that performs a dummy write operation, duringwhich no data is actually written to the optical disc, to ensure thatthe transmission rate of the host is adequate to prevent buffer run. Oneproblem with this method is that it takes twice as long to write thedata to the disc. Also, because hosts sometimes encounter non-repeatableproblems, the aforementioned method is not perfectly safe and the riskof losing expensive media due to buffer run errors is not completelyeliminated.

[0011] Therefore, an optical disc drive that can write dataconsecutively and normally to an optical media in multiple sessionswithout the loss of data succession is needed.

[0012] Even if logical data succession is ensured as described above,data cannot be normally reproduced without physical correspondence ofthe succeeding portions of data written in multiple sessions.

[0013] Usually, a frame gap of up to +/− 2 bits may be present withoutpreventing a conventional optical disc drive from properly reproducingdata from an optical disc. However, if a conventional optical disc driveattempts to write multiple sessions of data by selecting a writing startpoint based on a rotating control by a wobble synchronic signal, a framegap of scores of bits may result. Therefore, synchronization may be offin that portion and several frames of data may be lost.

[0014] Therefore, what is needed is an optical disc drive that is ableto correctly detect an end portion of data written in a preceding writesession so that an accurate write start point is provided for asucceeding write session.

[0015] Further, it is desirable that such an optical disc drive shouldbe able to detect the end portion of data written in a preceding writesession at low cost.

SUMMARY OF INVENTION

[0016] An object of the present invention is to provide an optical discapparatus characterized by writing means for maintaining data successionby halting CIRC encoding at the end of a preceding write session andresuming CIRC encoding at the beginning of a succeeding write session.

[0017] A second object of the present invention is to provide an opticaldisc apparatus characterized by a counter circuit for counting thechannel bit PLL (phase locked loop) which takes timing from the end ofpreviously written data to select a writing start point for a succeedingwrite session.

[0018] A third object of the present invention is to provide a countercircuit for counting a frame sync signal which takes timing from the endof previously written data to select a writing start point for asucceeding write session.

[0019] A fourth object of the present invention is to providecontrolling means for controlling the writing of data to an optical discdrive according to the present invention. The controlling means pauses awrite operation when data from the host has not been transmitted in timefor writing to the optical disc, and restarts the write operation whendata from the host computer is again available.

[0020] A fifth object of the present invention is to provide analternate controlling means for controlling the writing of data to anoptical disc drive according to the present invention. The alternatecontrolling means pauses a data write operation when data from the hosthas not been transmitted in time for writing data to the optical disc,reduces the write speed of the optical disc drive, and then resumes thewrite operation.

[0021] In accordance with the first object, the optical disc driveincludes a Pause circuit which masks the clock input to the encodersupon the generation of a Pause signal. This prevents the encoders fromfurther inputting and outputting data. Therefore, even if writing to theoptical disc occurs in multiple write sessions, data succession ismaintained.

[0022] In accordance with the second object, one embodiment of anoptical disc drive according to the present invention includes acounting circuit which counts the PLL signal derived from the channelbit. The PLL signal has the smallest error for previously written data.It is possible to calculate the end of the data based on this signal, sothat the correct writing start point for succeeding data write sessionsmay be selected.

[0023] Many inexpensive and widely used decoder LSIs which are used inknown optical disc drives do not output a channel bit PLL, but ratheroutput a frame sync signal and a sub code sync signal as a sub codeoutput. Therefore, in accordance with the third object, a secondembodiment of an optical disc drive according to the present inventionincludes a counting circuit which counts a frame sync signal and asub-code sync signal to select a writing start point for a succeedingdata write session. Accordingly, it is possible to detect the end of thepreviously written data at low cost.

[0024] In accordance with the fourth object, one embodiment of anoptical disc drive includes a processor for detecting when data from ahost stored in a data buffer is low, generating a pause signal forpausing a data writing operation, waiting until additional data isreceived from the host, and removing the pause signal so that the datawriting operation may resume.

[0025] In accordance with the fifth object, another embodiment of anoptical disc drive includes a processor for detecting when data from ahost stored in a data buffer is low, generating a pause signal forpausing a data writing operation, decreasing the write speed of theoptical disc drive, and removing the pause signal so that the datawriting operation may resume.

[0026] Because an optical disc drive according to the present inventioncan write in multiple sessions, a data interruption between the host andthe optical disc drive does not result in the loss of the media, therebyreducing the cost of operating the optical disc drive. Accordingly, alarge data buffer is not necessary, which also lowers the cost of theoptical disc drive. This ability to write in multiple sessions alsoeliminates the need for a test write operation to test the transmissionrate of the host computer, which saves time. It is also unnecessary fora user to be aware of the transmission rate of the host and the writerate of the optical disc drive, which simplifies operation of theoptical disc drive.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 is a hardware block diagram showing the structure of anoptical disc apparatus in accordance with one embodiment of the presentinvention.

[0028]FIG. 2 is a format diagram showing the format of CD-R or CD-RWdata on an optical disc.

[0029]FIG. 3 is a timing diagram showing an example of a possible timingsequence of plural write sessions for writing data in the format shownin FIG. 2.

[0030]FIG. 4 is a circuit diagram of a write control circuit in theoptical disc apparatus of FIG. 1.

[0031]FIG. 5 is a format diagram showing the positional relationship ofthe end data written in a preceding write session and start data writtenin a succeeding write session by a conventional optical disc apparatus.

[0032]FIG. 6 is a format diagram showing the positional relationship ofthe end data written in a preceding write session and start data writtenin a succeeding write session by optical disc apparatus according to thepresent invention.

[0033]FIG. 7 is a circuit diagram showing a circuit for generating awrite start signal at the end of previously written data, as shown inFIG. 6, according to one embodiment of the present invention.

[0034]FIG. 8 is a timing diagram showing the write timing of an opticaldisc drive using the circuit of FIG. 7.

[0035]FIG. 9 is a circuit diagram showing a circuit for generating awrite start signal at the end of previously written data, as shown inFIG. 6, according to a second embodiment of the present invention.

[0036]FIG. 10 is a timing diagram showing the write timing of an opticaldisc drive using the circuit of FIG. 9.

[0037]FIG. 11 is a flow chart showing one method for writing data to anoptical disc using an optical disc drive according to the presentinvention.

[0038]FIG. 12 is a flow chart showing a second method for writing datato an optical disc using an optical disc drive according to the presentinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0039] Preferred embodiments of the present invention will be describedwith reference to the accompanying drawings.

[0040]FIG. 1 is a hardware block diagram showing the structure of anoptical disc apparatus according to one embodiment of the presentinvention. The optical disc 1 is turned by the spindle motor 2. Thespindle motor 2 is controlled so as to keep constant linear velocity bythe motor driver 3 and the servo 4. The linear velocity can be changedstepwise. The optical pick-up 5 includes a semi-conductor laser, anoptical arrangement, a focus actuator, a photo detector, and a positionsensor. The optical pick-up radiates laser rays L on the recordingsurface of the optical disc 1.

[0041] The optical pick-up 5 can be moved in a seeking direction. Thefocus actuator, track actuator, and seek motor are controlled to locateand focus the laser beam L on a target point of the optical disc 1 bythe motor driver 3 and the servo 4 based on signals from the photodetector and position sensor of the optical pick-up 5.

[0042] When reproducing data, a reproducing signal obtained from theoptical pick-up 5 is amplified and digitized by the read amplifier 6 andinput to the CD decoder 7, where de-interleave and error correction arecarried out.

[0043] When the reproduced data is audio or music data, an analog audiosignal is derived by inputting the output data from the CD decoder 7into the D/A converter 12.

[0044] When the reproduced data is ROM data, the de-interleaved anderror-corrected data from the CD decoder 7 is input to the CD-ROMdecoder 8, and further error correction is carried out. After that,output data from the CD-ROM decoder 8 is stored in the buffer RAM 10 bythe buffer manager 9. When a complete sector of data is ready, the datais transferred to the host computer by the ATAPI/SCSI interface 11.

[0045] When data is to be written to the optical medium 1, the laserbeam must be positioned at the writing start point. The writing startpoint is searched by the wobble signal pressed beforehand in the form ofmeandering track. The wobble signal includes absolute time informationcalled ATIP. The ATIP information is derived by the ATIP decoder 13. Asynchronizing signal produced by the ATIP decoder 13 is input to the CDencoder 14, and it is possible to write data at an accurate position.

[0046] Data that is to be written to the optical disc 1 is received fromthe host computer through the ATAPI/SCSI interface 11. The data isstored in the buffer RAM 10 by the buffer manager 9.

[0047] Data writing begins once data is present in the buffer RAM 10.Error correction codes are added to the data, and CIRC encoding isperformed, by the CD-ROM encoder 15 and/or the CD encoder 14. The datais recorded on the target optical disc 1 through the laser controlcircuit 16 and the optical pick-up device 5.

[0048] Known optical disc drives cannot immediately begin reading UserData Blocks on an optical disc drive. In order for an optical disc driveto achieve synchronization and data interleave, lead in and lead outblocks are necessary. FIG. 2 shows a format that provides five lengthylead in blocks comprising a link block and Run In

[0049] Blocks 1-4 preceding the User Data Block, and two lengthy leadout blocks comprising Run Out Blocks 1 and 2 after the User Data block.

[0050] In order to prevent the aforementioned Buffer Run problem, theoptical disc apparatus of the present invention is capable of writinguser data in multiple write sessions. FIG. 3 illustrates an example ofwriting data in the format shown in FIG. 2 in multiple write sessions.The optical disc drive of the present invention receives data from thehost computer, and carries out Start Write when the buffer RAM 10 isfull of data. Start Write includes writing the lead-in and run-in blocksshown in FIG. 2.

[0051] When the optical disc drive starts to write the User Data Block,the data remaining in the buffer RAM 10 is reduced. If the amount ofdata in the buffer RAM 10 is below a preset level, a Pause signal isgenerated and the writing stops. The optical disc drive then waits foradditional data transmission from the host. When the buffer RAM 10 isagain full, Restart Write is carried out by removing the Pause signaland data is written from the position at which the writing was paused.When all data from the host computer is written to the optical disc 1,the Stop Write point is reached.

[0052] A conventional optical disc drive cannot write data in theaforementioned manner for two reasons. First, a conventional disc drivedoes not provide a mechanism for stopping the CD-ROM encoder 15 and CDencoder 14 (FIG. 1) when no data is present in the buffer RAM 10. Thus,when no data is present in the buffer RAM 10, the encoders continue towrite data, which changes the data format unit actually written on theoptical disc 1 from the logical data format received from the host.

[0053] The logical data format unit must conform, as prescribed by theOrange Book, to the physical data format unit on the optical disc. Ifthe encoder could be made to stop when data is not present in the bufferRAM 10, it would be easy to ensure that the physical data format unitson the optical disc 1 conform to the logical data format units from thehost.

[0054]FIG. 4 is a circuit diagram showing a circuit which controls datawriting by pausing the encoders when a pause signal, indicating that thebuffer RAM 10 is awaiting more data from the host, is received. When aPause signal is input to the circuit, the clock to the CD-ROM encoder 15and the CD encoder 14 is masked. Therefore, the CD-ROM encoder 15 andthe CD encoder 14 stop encoding and stop outputting Write Data.

[0055] The Write Gate signal is also masked by the Pause signal.Therefore, data writing for the optical disc stops also. The encodingdata in the RAM 21, 22 is maintained during the Pause. Then, when thePause signal in canceled, writing on the optical disc resumes with datasuccession maintained. The pause signal is highly synchronized to thepausing and resuming of the data writing.

[0056] The second reason why a conventional optical disc drive cannotwrite data in the manner described in FIG. 3 is that the writing startpoint of the laser beam L cannot be controlled with sufficient accuracyusing spindle motor controls based on the ATIP of the wobble signal.

[0057]FIG. 5 is a format diagram showing the positional relationship ofthe end data written in a preceding write session and start data writtenin a succeeding write session by a conventional optical disc apparatus.As shown in FIG. 5, a large data overlapping of 4 EFM (eight to fourteenmodulation) frames is possible with a conventional disc drive. Such alarge error can occur due to spindle motor controller errors. Thestarting position of the data writing in a conventional disc drive isselected based on the ATIP of the wobble signal without reference topreviously written data. When such a large error occurs, framesynchronization is out and it is impossible to reproduce data properlyeven for an optical disc such as a CD, which has high error correctioncapacity.

[0058] It is necessary, as shown in FIG. 6, to write succeeding datawithin a +/− 2 bit clock error. Thus, it is impossible to accuratelyposition the laser beam to the correct start location using aconventional optical disc drive with writing control based on thespindle motor control.

[0059] In contrast to known optical disc drives, the optical disc drivein accordance with the present invention locates the end of the datapreviously written. The end position is based on the clock used tosynchronize written data. The data writing start position is then basedon the end position.

[0060]FIG. 7 is a circuit diagram illustrating a circuit for generatinga write start signal at the end of previously written data (as shown inFIG. 6) according to one embodiment of the present invention. FIG. 8 isa timing diagram showing the write timing of an optical disc drive usingthe circuit of FIG. 7.

[0061] The circuit shown in FIG. 7 generates a write start signal bycounting the channel bit PLL signal. The channel bit PLL clock numberfrom the rising position of the sub code sync clock to the end positionof data frame 25 is set in the channel bit offset register 30. Thisnumber is decided by sub sync clock producing timing (hardware) of theCD decoder. Therefore, the value of the channel bit offset register 30cannot increase and decrease dynamically. The CD encoder reads the subcode of each frame and produces the sub code sync clock. However, decodedelay is a little different because of variable CD decoder chips.Therefore, a gap between the data and the phase of the sub code syncclock is produced. The channel bit offset register 30 adjusts the gap.The apparatus detects the address of the writing start sector 1 by theATIP or sub Q code, and loads the channel bit offset register 30 valueto the 16 bit down counter 31 on the first sub code sync, which is thesub-code sync of the writing start sector. The down counter 31 thendecrements on succeeding clock signals. Finally, when the 16 bit downcounter 31 reaches zero, it outputs RC (Reset Counter), which is used asthe Write Start signal.

[0062] Thus, it is possible to accurately start to write from the end ofthe data written during the preceding write operation. The write startsignal for the succeeding portion of data with the smallest possible gapis formed by using the channel bit PLL, which is the signal with thesmallest error.

[0063] Many inexpensive and widely used decoder LSIs used inconventional optical disc drives do not output a channel bit PLL signal.Rather, a frame sync signal and a sub code sync signal are output bythese decoders. It is also possible to use these signals to accuratelybegin writing succeeding data at the end of previously written data.

[0064]FIG. 9 is a circuit diagram showing a circuit for generating awrite start signal based on the frame sync and sub code sync signalsfrom the decoder 7 of the optical disc drive shown in FIG. 1. FIG. 10 isa timing diagram showing the relationship between the input frame syncand sub code sync signals and output write start signal obtained fromthe circuit shown in FIG. 9.

[0065] The circuit shown in FIG. 9 generates a start write signal bycounting the frame sync clock. The frame offset register 40 inputs theframe sync clock number from the sub code sync clock to a Fr25 framesync clock. The clock offset register 41 inputs the Write standard clocknumber from the Fr25 frame sync clock to the write start position.

[0066] Then, the address of the writing start sector 1 is detected byATIP or sub code. The frame offset register value is loaded to the 5 bitdown counter 42 by the first sync code, which is the sub code sync ofthe writing start sector. The channel bit offset register value isloaded to the 16 bit down counter 31.

[0067] When the 5 bit down counter 42 is decremented by the frame syncclock and becomes zero, it loads the value of the clock offset register41 to the 11 bit down counter 43. When the 11 bit down counter 43 isdecremented by the Writing standard clock and becomes zero, it outputsRC, which is the Write Start signal.

[0068] In this manner, it is possible to start to write accurately fromthe end of previously written data based on a count of the frame syncsignal. The frame sync signal can be obtained by an inexpensive andwidely used decoder LSI. Therefore, the cost of the optical disc drivecan be reduced.

[0069] The CPU 17, ROM 18 and RAM 19 (FIG. 1) are used to control writeoperations for the optical disc drive according to one of two methods.One such method is shown in FIG. 11. When writing is to start, the linkblock and four run-in blocks are written to the disc at step S1. Userdata in the buffer is written to the disc as step S2. This is the normalwriting sequence which starts from the link and run-in blocks.Additional data is received from the host at step S3. At step S4, theamount of data in the buffer is determined to determine whether a bufferrun error may be occurring.

[0070] If the data in the buffer from the host is not low in step S4,the buffer is checked to determine whether the data is complete at stepS5. If data writing is not complete, the data writing continues at stepS2. If the data writing is complete, Stop Write occurs at step S6, andthe write operation is complete. Stop Write is normal sequence ofwriting the Run out blocks.

[0071] If the data from the host is low in the step S5, a Pause Writesignal is generated to pause the write operation at step S7 while moredata is received from the host at step S8, thereby preventing a bufferrun condition. The content of the buffer is checked at step S9. If thebuffer is not full at step S9, additional data is received at step S8.When the buffer is full, writing resumes at step S10 without writing anylink blocks, thereby maintaining data succession. The writing operationcontinues at step S3.

[0072] In this manner, when the data transmission from the host is notin time during write operations to the optical disc, the data writingstops. When the data is fully sent from the host, the write operationresumes.

[0073] Accordingly, when the data transmission from the host ismomentarily interrupted, or the transmission rate is reduced, it ispossible to write data on the optical disc by dividing the writeoperation into a plurality of write operations. Data writing failurescan thus be prevented. The size of the buffer RAM necessary forabsorbing data transmission rate variations can therefore be reduced,thereby reducing the cost of the optical disc drive.

[0074] A second method for controlling the write operation of an opticaldisc drive according to the present invention is shown in FIG. 12. Inthis method, the Start Write operation is carried out at the speed setby the host, or at the maximum speed of the disc drive if no speed isspecified by the host, at step S11. Data is written to the optical discat step S12. Additional data is received from the host at step S13. Theamount of data in the buffer is determined at step S14. The buffer maybecome depleted for the reasons discussed earlier.

[0075] If the data in the buffer from the host is not low at step 14, itis determined whether the data has completed at step S15. If the datahas not completed, data writing continues at step S12. If the data hascompleted, Stop Write is carried out at step S16 and the writingoperation is complete.

[0076] If the data from the host is low at step 14, a Pause Write isgenerated at step S17 so that writing on the optical disc pauses. Then,additional data from the host is received at step S18. When the bufferis full at step S19, the optical disc drive recording speed is loweredone step at step S20 if the speed is not already at the minimum. Thepause signal is removed at step S21, and the write operation continuesat step S13 without writing any link blocks and maintaining datasuccession.

[0077] In this manner, when the data transmission rate from the host isless than the data writing rate of the optical disc, the data writingstops, the writing rate of the optical disc is stepped down, and datawriting resumes.

[0078] Accordingly, the optical disc drive continues writing data afterautomatically changing the data writing speed in response to the datatransmission rate from the host. Therefore, it prevents excessively longdata writing operations caused by repeated Pauses. Further, a user doesnot have to check the data transmission capacity of the host and thewriting speed of the optical disc driver. Therefore, the write operationis simple, and it is possible to write the data at the maximum capacityof the host.

[0079] The entire disclosure of Japanese Patent Application No.8-206705, filed Aug. 6, 1996, is expressly incorporated herein byreference.

[0080] The above description and drawings are only illustrative ofpreferred embodiments which can achieve and provide the objects,features and advantages of the present invention. It is not intendedthat the invention be limited to the embodiments shown and described indetail herein. Modifications coming within the spirit and scope of thefollowing claims are to be considered part of the invention.

What is claimed as new and desired to be protected by Letters Patent ofthe United States is:
 1. An optical disc apparatus for recording andreproducing data for a data recording medium, wherein said optical discapparatus includes writing means for maintaining data succession byCross-Interleaved Reed-Solomon Code (CIRC) decoding in a start portionand an end portion of data written on the optical recording medium.